Earth and the Moon

Viewing Non-Stellarnight Sky Objects

What do comets and asteroids look like in the night sky?

Comets look like fuzzy structures in the sky that are much larger than stars. A very bright comet, easily visible to the unaided eye, typically appears only once every few years; its coma is usually about the size of a small coin held at arm’s length or smaller, whereas its tail can be much longer. Depending on its orbit, the comet could move across the sky in as quickly as just a week or so, or it could linger for months.

Asteroids are small and faint, and are rarely if ever visible to the unaided eye. Even when astronomers can find asteroids using large telescopes, it can be very challenging to track them across the sky because of their rapid motion. Meteors, on the other hand, regularly fall through the atmosphere and leave ethereal, visible trails for fleeting moments; a few meteors are typically visible in dark-sky sites each night, while dozens or hundreds may be visible during meteor showers.